HDU1754 I Hate It (Splay)

题意：中文题。。。

以前用线段树写过。。现在学Splay，也来写一下。。

用伸展树来进行单点更新和区间查询，单点更新就直接查选第k个直接查选到这个点然后再维护上去就可以了，，区间查选，因为这里是闭区间，所以要先把区间扩大一下（自己用手写下就知道），然后第k个找到左边界的点，旋转到根，找到右边界的点旋转到根的右子树，然后右边界的点的左子树就是要找的答案了。。

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int MAXN=222222;
struct Node
{
	Node *ch[2];
	Node *pre;
	int size,val,mx;
}p[MAXN];
int num[MAXN];
int tot;
Node *null=&p[0];
Node *root;
Node *new_Node(int val)
{
	Node *rt=&p[++tot];
	rt->val=val;
	rt->size=1;
	rt->ch[0]=null;
	rt->ch[1]=null;
	rt->pre=null;
	return rt;
}
void pushup(Node *rt)
{
	rt->mx=max(rt->val,max(rt->ch[0]->mx,rt->ch[1]->mx));
	rt->size=rt->ch[0]->size+rt->ch[1]->size+1;
}
Node *build(int l,int r)
{
	if(l>r)
		return null;
	Node *rt;
	int mid=(l+r)>>1;
	rt=new_Node(num[mid-1]);
	rt->ch[0]=build(l,mid-1);
	rt->ch[0]->pre=rt;
	rt->ch[1]=build(mid+1,r);
	rt->ch[1]->pre=rt;
	pushup(rt);
	return rt;
}
void Rotate(Node *x,int c)
{
	Node *y=x->pre;
	y->ch[!c]=x->ch[c];
	if(x->ch[c]!=null)
	{
		x->ch[c]->pre=y;
	}
	x->pre=y->pre;
	if(y->pre!=null)
	{
		if(y->pre->ch[0]==y)
			y->pre->ch[0]=x;
		else
			y->pre->ch[1]=x;
	}
	x->ch[c]=y;
	y->pre=x;
	if(y==root)
		x=root;
	pushup(y);
	pushup(x);
}
void splay(Node *x,Node *f)
{
	while(x->pre!=f)
	{
		if(x->pre->pre==f)
		{
			if(x->pre->ch[0]==x)
			{
				Rotate(x,1);
			}
			else
			{
				Rotate(x,0);
			}
		}
		else
		{
			Node *y=x->pre,*z=y->pre;
			if(z->ch[0]==y)
			{
				if(y->ch[0]==x)
				{
					Rotate(y,1);
					Rotate(x,1);
				}
				else
				{
					Rotate(x,0);
					Rotate(x,1);
				}
			}
			else
			{
				if(y->ch[1]==x)
				{
					Rotate(y,0);
					Rotate(x,0);
				}
				else
				{
					Rotate(x,1);
					Rotate(x,0);
				}
			}
		}
	}
	pushup(x);
}
Node *kth(Node *rt,int k)
{
	if(rt->ch[0]->size+1==k)
		return rt;
	if(k<=rt->ch[0]->size)
		return kth(rt->ch[0],k);
	else
		return kth(rt->ch[1],k-(rt->ch[0]->size)-1);
}
int main()
{
	int n,m,i;
	Node *L,*R;
	while(scanf("%d%d",&n,&m)==2)
	{
		for(i=1;i<=n;i++)
			scanf("%d",&num[i]);
		tot=0;
		num[0]=0;
		num[n+1]=0;
		root=build(1,n+2);
		char op[2];
		int x,y;
		while(m--)
		{
			scanf("%s%d%d",op,&x,&y);
			if(op[0]=='Q')
			{
				y+=2;
				L=kth(root,x);
				R=kth(root,y);
				splay(L,null);
				splay(R,L);
				printf("%d\n",R->ch[0]->mx);
				root=L;
			}
			else
			{
				x++;
				L=kth(root,x);
				splay(L,null);
				root=L;
				root->val=y;
				pushup(root);
			}
		}
	}
	return 0;
}